L = 1/2*ρ*v*v*A*CL

L is lift force,
ρ is air density
v is true airspeed,
A is planform area, and
CL is the lift coefficient at the desired angle of attack, Mach number, and Reynolds number

Conveyor speed = Plane speed

Vc = Vp

v = true airspeed = Vc-Vp = 0

L = 1/2*ρ*0*0*A*CL = 0 = No lift = No take off.